Remote control is a popular feature in television receivers. One of the functions often the subject of remote control is the audio output of the receiver. In conventional all-electronic remote systems the audio volume is varied by varying the gain of a DC gain-controlled audio amplifier. In digital gain control systems this can be accomplished by transmitting an acoustic signal to a remote receiver. Depending on the frequency of the acoustic signal, a clock oscillator is enabled and provides a pulse train to an UP/DOWN counter. The counter can be made to count either up or down, again depending on the frequency of the acoustic signal. The counter output is coupled to a digital-to-analog (D/A) converter which develops an analog DC signal used to establish the gain of the amplifier.
Conventional DC gain-controlled circuits tend to have an S-shaped characteristic. That is, in order to cause a given change in gain, greater increments in control signal are required at the extremities of the gain-control range than are required over the central portion. As a result, the operator of a remote transmitter tends to feel a loss of control or an excessive time lag between the activation of the transmitter and a noticeable change in audio volume, at both the minimum and maximum levels of volume.